Electric lamp and base construction



July 13, 1954 E K ELECTRIC LAMP AND BASE CONSTRUCTION Filed Sept. 1, 1951 Inventor: Charles E. BecK F l .a il- H|s Attorney Patented July 13, 1954 UNITED STATES PATENT OFFICE ELECTRIC LAMP AND BASE CONSTRUCTION Liber U-238, page 394 Application September 1, 1951, Serial No. 244,753

3 Claims.

This invention relates generally to bulbs for incandescent lamps and similar electrical devices, and more particularly to an improved neck construction for such bulbs which facilitates the making of a base or shell contact. The invention is also concerned with the means for making the connection between the side lead-in wire of the lamp and the shell or cylindrical portion of the base.

In the manufacture of electric lamps, particularly of household type incandescent lamps, it has become standard practice to employ a base comprising a metallic shell having its cylindrical surface threaded and provided with an end contact or eyelet insulated from the base proper. base is applied to the bulb neck, that is to the constricted and generally cylindrical extension of the main spherical portion of the bulb, and may be cemented to it or mechanically secured by interlocking protuberances and indentations in the base and neck respectively. In order to provide external contact surfaces for energizing the filament of the lamp, one of the lead-in wires is connected to the end contact or eyelet, and the other is connected to the side wall or shell of the base.

Various means have been proposed in the past for effecting the connection between the lead-in wires and the base. It will be understood that two connections must be made, one between the end contact or eyelet of the base and the top lead-in wire, and the other between the shell or cylindrical portion of the base and the side lead-in wire. The present invention is more particularly concerned with the means for effecting the latter I connection. The more common practice up to the present has been to use a readily soldered metal for the shell of the base and to solder the connection to the side lead-in wire. This soldering operation is a relatively costly procedure, particularly from the standpoint of the time and the maintenance required in connection with the soldering mechanisms of the automatic machines used in the mass production of incandescent lamps. Moreover it is highly desirable to eliminate the soldering operation entirely in view of the high cost of readily soldered metals such as copper or brass, and the comparative low cost of other metals such as aluminum which cannot be soldered readily.

In the manufacture of bulbs for incandescent lamps, there occurs the sealing operation which consists of uniting what is termed a stem or mount, including a glass flare tube, to the neck portion of a bulb. In addition to the sealing This operation, it is desirable to shape the united parts while still plastic from the sealing-in fires, so that, when completing the lamp, the base may be more readily applied and held in fixed relation to the bulb.

An object of the present invention is to provide an improved electric lamp bulb wherein the neck portion has a particular configuration facilitating the attachment thereto of a base.

Another object of the invention is to provide an improved electric lamp construction which permits the making of a firm contact connection between the side lead-in wire and the shell of the base.

In accordance with the invention, the above objects are effected by shaping the neck of the vitreous bulb to a slightly elliptical or oval cross section in the region where the skirt of the base seats against the neck of the bulb. During the assembly of the lamp, the side lead-in wire is caught between the seal of the bulb and the shell of the base across the wider diameter of the seal. This results in a firm electrical contact because a slight elliptical deformation of the base necessarily occurs which assures a resilient contact, and prevents subsequent loosening of the connection in the finished lamp.

For further objects and advantages and for a better understanding of the invention, attention is now directed to the following description and accompanying drawings. The features of the invention believed to be novel will be more particularly pointed out in the appended claims.

In the drawings:

Fig. 1 is a side sectional view through the lower portion of a finished incandescent lamp embodying the invention, and showing the neck of the bulb with a conventional screw type base fastened thereto.

Fig. 2 is a cross sectional view of the lamp of Fig. l, seen along the section lines 2-'2.

Fig. 3 is a simplified illustration of a mechanism by means of which a bulb for an incandescent lamp may be provided with a seal in accordance with the present invention.

Fig. 4 is a plan view of the dies used with the mechanism of Fig. 3 for molding the seal.

The invention will be described with reference to an Edison screw base of the type which is widely used for household incandescent lamps. It will be understood however that the invention is equally applicable to bases of a diiferent type from this; for instance the invention may be applied to bases of the bayonet type wherein it is desired to effect a. connection between the side lead-in wire and the straight-walled cylindrical shell of the base.

The internal construction and the manner of fastening the base in the case of a screw type incandescent lamp is illustrated in Fig. 1. The base I is mounted on the constricted lower portion or neck 2 of an evacuated glass bulb of which a fragment is shown at 3. The bulb may be of conventional construction and containing a filament mounted within it on the ends of the lead-in wires 4 and which enter the bulb through a glass press 6.

The base i proper comprises a threaded metal shell I, an insulating body or web 8, and an end contact 9 fastened to the lower surface thereof. The insulating web 3 may be made of glass in accordance with the common practice or it may be made of a thermal setting plastic. The base is shown herein fastened to the neck of the bulb by means of a suitable cement as indicated at l0, but it may equally well be fastened mechanically by means of notches in the shell of the base fitting into corresponding indentations in the neck of the bulb.

The contact surfaces for the lead-in wires 4 and 5 are provided by the end contact 9 and the shell I of the base respectively. The connection to the end contact or eyelet may be made in the usual manner by soldering, as indicated at H, or in any other suitable manner.

The invention is more particularly concerned with the means whereby the connection between the side lead-in wire 5 and the shell I of the base is effected. As illustrated in Fig. 1, the neck 2 comprises an end portion I2 which is generally annular and perpendicular to the axis of the bulb. This portion is formed by the fusing of the edge of the fiare tube 13 with the lower edge of the neck during the molding operation. Immediately adjacent the annular portion i2, is a generally cylindrical portion [4 of a diameter slightly less than the root diameter of the threads of the base in order to permit the disposition of the cement If! therebetween. As illustrated in the drawing, indentations or notches l5 may be provided in cylindrical portion Hi to improve the bond between the bulb neck and the basing cement. The straight cylindrical portion M merges into the bulb through an expanded cylindrical portion 16 and a conical shoulder or fiaring portion IT.

The connection between the side lead-in wire 5 and the shell 1 of the base occurs at [8 by reason of the tight fit between the skirt of the shell and the expanded cylindrical portion It at that point. If desired, the end of the side lead-in wire 5 may be cut off and bent back into the skirt of the shell as indicated at 19, in order to provide the lamp with a neat and finished appearance. Alternatively, the lead wire may be merely cut off very short at that point and brushed back sideways into the slit between the shoulder I! and the flared edge of the base.

In accordance with the invention, the expanded cylindrical portion i6 is provided with a slightly oval cross section as illustrated in Fig. 2. The eccentricity has been somewhat exaggerated in the drawing, for greater clarity. It has been found that where reliance is placed upon a tight fit between the neck of a bulb and the skirt of its base in order to effect a contact connection between the side lead-in wire and the shell, a relatively large number of defective lamps occur. The reason for this is that the wire is quite fine, and if there is a m appreciable dimensional variation in either the expanded portion [6 of the neck of the bulb or in the skirt of the base, either a loose fit will occur and the connection will be intermittent, or a tight fit will prevent the base from seating squarely on the bulb. Since both the bulbs and the bases are mass produced, dimensional variations will unavoidably occur, and it is generally not feasible to attempt to reduce these variations in order to assure in all cases the manufacture of a satisfactory incandescent lamp such as described herein. In the case of the bases particularly, they are made through a drawing operation which leaves considerable room for variations. Under certain circumstances, the actual circumference of any one base may vary by as much as 5 percent from the mean or design circumference. The solution to these problems in accordance with the invention is found in making the portion l6 slightly oval or elliptical in transverse section.

Referring to Fig. 2, the diameter A is made slightly larger than the diameter B. As a result, when the base is fitted over the neck of the bulb, a slight elliptical deformation of the skirt of the shell occurs assuring a tight fit and a firm con tact between the side lead-in wire and the shell. If the shell of the base is slightly oversize, it merely suffers less deformation than in the normal case, and if it is undersize, it suffers slightly more deformation. This construction also has the advantage that a firmer contact is achieved because the shell, due to its resilient nature, tends to spring back into place, that is to return to its normal cylindrical configuration, and thereby effects a continuous pressure against the lead-in wire.

In general, it appears undesirable to provide the cylindrical portion It with an eccentricity greater than 10 percent; that is the larger diameter A must not be more than 10 percent greater than the smaller diameter B. The reason for this is that an eccentricity in excess of 10 percent would cause binding of the base when the lamp is screwed into a socket. In general, I have found that an eccentricity of about 5 percent is entirely satisfactory and assures practically satisfactory lamp production using parts having only the normal tolerances. As an example merely, in the case of a 60 watt household type incandescent lamp, the design diameter or inside dimension of the skirt of the base is 1.000 inch. The bulb was made with an oval portion in the seal wherein the major diameter A was 1.010 inch and the minor diameter B was 0.953 inch, the diameter of the base thus being intermediate the major and minor diameters of the oval seal portion. The difference between the maximum and minimum diameters was thus .057 inch, or in other words an eccentricity between 5 and 6 percent. Such a construction was found to reduce shrinkage, that is loss in the manufacturing process, to a negligible figure, assures a firm contact, and does not cause any binding when the lamp is screwed into a standard socket.

The oval cross section of the seal may be achieved during the operation of uniting the stem to the neck portion of the bulb, for instance by a mechanism such as is described in United States Patent 2,306,231 Malloy et al., issued June 25, 1935, and assigned to the same assignee as the present invention. As described therein, the de sired configuration of the neck is obtained by blowing air into the bulb while its neck portion is still plastic from .the sealing-in fires. Referring to Fig. 3, the bulb 3 has its neck portion located within a pair of confining dies 28 and 2!, more fully shown in Fig. 4. These dies may be mounted on suitable supporting members, whereof frag ments are indicated at 22 and 23. The members pivot in laterally to encompass the neck of the bulb when it is indexed into place. The bulb may be supported by its exhaust tube 25 on a holder 25 which also permits the making of a connection to a supply of compressed air at 26. The member 2? is provided for the purpose of pressing down on the bulb and seating it firmly in the dies 20 and 2|. Since the lower portion of the bulb is still plastic from the sealing in fires, as soon as compressed air is admitted into it through the connection 25, the neck immediately expands to the configuration defined by the dies 29 and 2|. It will be seen in Fig. 4 that the dies are merely two half-sections which define, when pivoted together, the final desired shape or outline of the neck portion of the bulb. The small ventilating holes 28 in the dies prevent the trapping of any air between the dies and the neck of the bulb when its expansion takes place.

In order to make the indentations or notches in the reduced cylindrical portion I of the neck, a pair of small rounded pins may be disposed within the dies as shown at 29 in Fig. 4. If desired, these pins may be located so as to make the indentations along a predetermined diameter or" the neck, for instance along the major diameter. In such case, the operator in assembling the base of the bulb, will immediately be made aware of the location of the major diameter against which the side lead-in wire is required to be caught in order to achieve a firm electrical connection.

While a certain specific embodiment has been shown and described, it will of course be understood that various modifications may be made without departing from the invention. Thus the invention is equally applicable to screw type bases such as has been described, or to bayonet type bases wherein it is desired to make a connection between one of the lead-in wires and the shell or straight-wall portion of the base. The appended claims are therefore intended to cover any such modifications coming within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric lamp comprising a vitreous bulb having a main portion and a neck portion of reduced diameter and generally cylindrical form, lead-in wires sealed into said bulb through said neck portion, and a cylindrical base fastened on said neck portion, said neck portion being oval in a transverse section corresponding substantially to the plane of its engagement with the skirt of said base, and one of said lead-in wires being caught between said skirt and said neck portion across the greater diameter of said section.

2. An electric lamp comprising a vitreous bulb having a main portion, a neck portion of reduced diameter and generally cylindrical form, an intermediate portion of oval cross section joining said neck portion to the main portion of the bulb, lead-in wires sealed into said bulb through said neck portion, and a cylindrical base fastened on said neck portion and having an edge seating on said expanded portion, one of said lead-in wires being caught between said base and said intermediate portion across its greater diameter.

3. An electric incandescent lamp comprising a vitreous bulb having a main portion, a neck portion of reduced diameter and generally cylindrical form, an intermediate portion of expanded diameter and oval cross section joining said neck portion to the main portion, lead-in wires sealed into said bulb through said neck portion, and a cylindrical base fastened on said neck portion and having a skirt seated on said expanded portion, one of said lead-in wires being caught between said skirt and said intermediate portion across its greater diameter, and said base having an inside diameter proportioned to cause a slight elliptical deformation thereof when seated on said expanded portion.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,420,831 McGowan May 20, 1947 FOREIGN PATENTS Number Country Date 609,031 Germany Feb. 6, 1935 727,578 Germany Nov. 6, 1942 

